4E analysis on a hybrid sustainable and decarbonised system for LNG cold energy recovery

To overcome the issue of temperature–energy grade mismatch and low cold exergy utilization efficiency in single-stage liquefied natural gas (LNG) cold energy recovery, this work proposes a hybrid system that combines a three-stage cold energy utilization with the complete Allam cycle carbon capture. The staged cold energy sequentially supports air separation for oxygen production, bottoming organic Rankine cycle (ORC), and flue gas liquefaction in the Allam cycle. Results indicate that the Allam-ORC combined cycle achieves a net power output of 58.87 MW (net electrical efficiency 84.8 %), with LNG cold energy utilization rate, cold exergy efficiency, and system exergy efficiency reaching 93.8 %, 46.8 %, and 63.8 %, respectively. The levelized cost of electricity decreases to 34.45 $·MWh−1, yielding net present values of 303.45 million $ (payback period of 4.03 years) and 5.90 billion $ (payback period of 0.26 years) without/with air separation unit revenue. Moreover, CO2 emission reduction reaches 28.06 t h−1 with a negative carbon index of 0.46 t h−1. Parametric optimization elevates cold exergy efficiency to 53.4 %, which could achieve a net electrical efficiency of 87.6 % that outperforms other Allam-integrated systems by 22.7 %–36.1 %, with electricity cost reduced by 42.8 % relative to LNG-Allam system. The proposed system, through synergistic optimization of cold energy cascade utilization and carbon capture, may provide a system solution with industrial application potential for low-carbon transformation of LNG industry chains.